Aluminium sailboat. Water in rudder

[xslim]

Hi guys,
I have an old 39ft aluminum sailboat.
this year project is to change all thruholes, new bottom paint, etc.

After I cleaned the boat from barnacles I noticed a bolt on the bottom of the rudder (big aluminium rudder on full skeg, tiller handling on top)

After undoing the bolt, the water started coming out and I heared a air sucking somewhere on top of rudder. From the amount of water that drained - probably 50l, I'm guessing the rudder is hollow.

Now the question is - I know it is bad to have water in foam cored GPR rudder, but is it bad having it in fully aluminium rudder?

[xslim]

Picture of a boat:

[UNCIVILIZED]

In a word. Yes

[model 10]

That drain plug is good for 2 things, tells you have water and a way to drain it out. I would want to know where it's comming from. If it's a few pin holes that's one thing but a crack is another.
Nice looking hull.

[noelex 77]

Fibreglass rudders very commonly leak because it is difficult to achieve a long term waterproof seal between the generally metal (stainless steel or aluminium) rudder shaft and the fibreglass skin.

On aluminium boats the junction between the aluminium shaft and the rudder skins can be welded forming what should be a permanent waterproof joint with no water in the rudder, ever. The rudder is always hollow on aluminium sailboats.

The good news is that marine grade aluminium does not corode in the presence of oxygenated seawater. So in some ways water in the rudder is not of great concern. There should be no dissimilar metals. With stagnant seawater there is a slight risk of crevice corrosion, but in general the water is likely to have done little or no harm, providing it has never frozen. There is a risk in NL that this is fresh water, and that it has frozen at some stage.

However, the bigger problem is why has the rudder leaked? This suggests a crack in the skin, or between the rudder itself and the shaft. This needs investigating so I am afraid it is time to drop the rudder and see where the water has entered, and why.

As a simple test, before dropping the rudder, you could slightly pressurize the drain hole with air from a foot pump (don't overdo this) and with some soapy water see where the rudder is leaking.

[Matt Johnson]

For some reason, the steering quadrant was bolted on our rudder instead of welding... and being exposed, it allowed water in. The rudder has holes in the bottom to allow water to enter/exit. It's been like this for 33 years and when we had the surveyor ultrasound it two years ago, it had zero deterioration.

Matt

[Panope]

Water in the rudder could potentially be a good thing as it would prevent the rudder from "floating" (if filled with air) when heeled. Might reduce weather helm pressure a touch.

Steve

[estarzinger]

Op - it is not terrible to have water in there - probably not doing any great harm, but it is also probably not "correct". I would follow the "soapy procedure" - cover rudder with very soapy water, pump air up bolt hole, look for soap bubbles being blown, get crack/pinhole welded closed.

Most aluminum rudders are hollow (air filled), I suspect your was, but some were designed to be oil filled - that eliminates corrosion concern, and is relatively neutral buoyancy. But it also can leak out and make a mess.

[BruceS]

If totally air tight what is going to happen in warmer waters or going to the North pole? Mercruiser legs have a small hose back into the hull to allow pressure 'relief'.
Reminds me of physics at school and the crushed gallon tin.............

[Jim Cate]

Originally Posted by BruceS

If totally air tight what is going to happen in warmer waters or going to the North pole? Mercruiser legs have a small hose back into the hull to allow pressure 'relief'.
Reminds me of physics at school and the crushed gallon tin.............

What's gonna happen? Not much, that's what! The pressure change from changes in the water temperature will be very small compared to the strength of the rudder structure. I suspect the pressure relief in the i/o legs have more to do with avoiding water intrusion into the gear oil than worries about crushing or blowing up!

Jim

[hpeer]

Originally Posted by funjohnson

For some reason, the steering quadrant was bolted on our rudder instead of welding... and being exposed, it allowed water in. The rudder has holes in the bottom to allow water to enter/exit. It's been like this for 33 years and when we had the surveyor ultrasound it two years ago, it had zero deterioration.

Matt

Matt,

Just took a quick peak at your blog. I recall sitting in that boat with my Wife and she asked my my opinion. I recall saying ....

Honey, I'm afraid if we buy this boat 2 years from now we will be sitting right here crying."

Good on you and yours for the job you've done. I have tremendous respect for your tenacity.

Cheers!

[Matt Johnson]

Originally Posted by hpeer

Matt,

Just took a quick peak at your blog. I recall sitting in that boat with my Wife and she asked my my opinion. I recall saying ....

Honey, I'm afraid if we buy this boat 2 years from now we will be sitting right here crying."

Good on you and yours for the job you've done. I have tremendous respect for your tenacity.

Cheers!

Thanks Hpeer. Next time I'll do a new hull instead of a rebuild. Its been way more work than it should have been had I not had to repair years and years of neglect.

Matt

[estarzinger]

Originally Posted by BruceS

If totally air tight what is going to happen in warmer waters or going to the North pole? .

There are a lot of similar "air tight" rudders sailing around (including Hawk's) and they dont suffer any pressure problems.

In fact part of our QA procedure (and for many metal boats) on the build was to pressure all sealed areas, which included the tanks, rudder, small prop skeg, keel envelop, bow crash box. They were all pressure tested (I think 5psi, but may be wrong about that was long ago) and had to hold it for 24 hours. That in fact was why we had a threaded bolt hole on these areas - to seal the port what was used for the air hose.

[Qayaq]

Hiya, my job these days is running 21 fast ferries through annual refit and survey.
We get heaps of corrosion problems, having sea water running through the rudder would be one thing, having stagnant seawater in it would likely lead to a badly corrosive enviroment. I would put a large hole saw though the skin and have a look inside, you can get the hole plugged welded back up if all is well. We use 3 psi for pressure testing, would also be careful of grinding back welds to flush to prevent cracking. Best of luck.

[xslim]

Thank you guys for all responses!
The water in rudder was salt, and last year the boat was in brekish water, so I believe the rudder leaked long ago.
The water was clear when coming out, so I hope there is no major corrosion inside.

I do plan to drop the rudder anyway - to change the bearings.

Steve, Any more info on weather helm?
My boat is 12m with a tiller, so this is quite interesting question.